1. Field of the Invention
The present invention relates to an assembly of parts to be formed into a T-joint weld that is applicable to manufacturing of an impeller in a compressor or the like.
2. Description of the Prior Art
Heretofore, upon welding an impeller in a compressor, an assembly of the parts to be formed into a T-joint weld as shown in FIG. 5 has been employed. In FIG. 5, reference character (a) designates a lower plate, reference character (b) designates a rib provided on the lower plate (a), reference character (c) designates an upper plate, and reference character (d) designates a beveling provided in the upper plate (c). The above-mentioned rib (b) has a thickness which gradually increases from its thin portion of about 2 mm in thickness to its thick portion of about 8-10 mm in thickness, and the width of the opening in the above-mentioned beveling (d) changes linearly in accordance with the variation of the thickness of the rib (b), so that width of the overlapped part of the rib (b) and the upper plate (c) is nearly constant over the entire length of the rib (b).
In the case where the thickness of the rib (b) increases from its thin portion of about 2 mm in thickness to its thick portion of about 8-10 mm in thickness and on the other hand the width of the rib (b) overlapped by the upper plate (c) is nearly constant over the entire length of the rib (b) as described above, even if the welding condition is changed depending upon the thickness of the rib (b), there still remain the following problems. That is, even if the thin-walled portion of the rib (b) is welded under a small current welding condition, since this portion of the rib (b) has a poor heat transfer capability, heat is accumulated in that portion of the rib (b), and hence the thin-walled portion of the rib (b) has a deep weld penetration as illustrated in FIG. 6(I).fwdarw.FIG. 6(II), weld metal (e) melts and falls, and so, penetration beads cannot be formed. Moreover, in the middle portion of the rib (b) where its thickness increases successively, there exists the problem that it is necessary to control the welding condition precisely and continuously in accordance with the thickness of the rib (b) and hence control of the welding condition becomes troublesome.